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Epson Toyocom heralds QMEMS process

Posted: 25 Nov 2008 ?? ?Print Version ?Bookmark and Share

Keywords:QMEMS? oscillator MEMS? quartz crystal piezoelectric?

MEMS oscillators use IC processing techniques to craft mechanical resonators that can be tethered inside a silicon chip. Traditional quartz oscillators require the cutting and beveling, but would be smaller in size, more immune to temperature drift, lower in price and in power consumption using photolithography techniques.

Epson Toyocom, which claims 23 percent of the global quartz oscillator market, reports it has perfected a semiconductor-like photolithography process called Quartz MEMS (QMEMS) that it claims will keep it ahead in the silicon MEMS oscillator market.

Specifications for the QMEMS process were said to be comparable or superior to competitors' MEMS oscillators, including those made by SiTime Corp., Discera Inc., Silicon Clocks Inc. and Mobius Microsystems Inc.

"MEMS traditionally refer to a silicon process, so that's why we call ours 'QMEMS', because ours are made from quartz, not silicon," said Debbie Word of Epson Toyocom. "We are using quartz wafers in a semiconductor-like fab, using a process involving photolithography, etching, metallization and sacrificial-layer removal--the same steps you take with silicon MEMS chips. But we are using the quartz material."

Piezoelectric quartz crystal oscillators have become standard since running a small current through them generates oscillation at a predictable frequency. The oscillations can be made immune to drift by compensating for temperature changes inside a package. Quartz, the most abundant piezoelectric material on Earth, is crafted to oscillate at a specific frequency through precision cutting and beveling.

Shrinking process
Several years ago, Epson developed a photolithography process to shrink tuning-fork resonators below 2mm, the point at which traditional cutting and beveling no longer worked. That process is being used for QMEMS oscillators, resulting in specifications rivaling silicon MEMS oscillators.

Market analysts claim the change will make little difference to OEMs.

"MEMS and other non-traditional solutions became viable because they brought increased functionality at a lower cost," said MEMS analyst Roger Grace. "Engineers are looking for the best possible solution, so if a QMEMS timing chip can provide their needed functionality at the lowest cost, then it will be successful regardless of the process they are using to make it."

Epson Toyocom also plans to make atmospheric pressure sensors using the QMEMS process, and has already used the process to create an ultrasmall (2mm x 2mm) gyroscopes for image stabilization in digital cameras.

- R. Colin Johnson
EE Times

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